Unlike the regular valve conduit, this valve has three possible settings: Closed (dark), only let vis through (light blue), and only let taint pass (dark purple).
Is clasified as Tainted Knowledge
Secondary click switch between each state : Only Vis > Only Taint > closed > Only Vis
Redstone signal makes the valve closed but it remembers the last state when the signal is removed.
These are the ultimate in Vis/Taint separation: extremely efficient. Hook a normal Vis Conduit up to your crucible, create a 'fork' and have an Advanced Vis Valve at each end. Set one to allow only Vis, the other to allow only Taint. Connect some (Advanced) Tanks to each end, and now you can enjoy pure samples of each without any more effort than just smelting stuff in your crucible.